1. Field of the Invention
This invention relates to the production of hydrocarbon solvents and is particularly concerned with a process for the simultaneous manufacture of naphthenic solvents and low aromatic mineral spirits.
2. Description of the Prior Art
Recent regulations restricting the use of aromatic hydrocarbons under conditions which may result in the loss of such hydrocarbons to the atmosphere have led to a demand for solvents which are essentially free of aromatic constituents. The relatively low solubility of many materials in normal paraffins and isoparaffinic hydrocarbons suggests that many such applications might be best served by the use of naphthenic solvents which generally have solvency values intermediate those of paraffins and aromatics. Large supplies of naphthenes are not readily available. It is known that aromatic compounds can be concentrated by extraction or adsorption on solid surfaces and then converted into naphthenic materials by hydrogenation. Processes for the manufacture of naphthenic solvents by this route pose problems, however, because of the highly exothermic nature of the aromatics hydrogenation reaction. The amount of heat released when aromatic concentrates are hydrogenated is so great that reactor temperatures become excessive unless integral cooling is employed, staged reactors provided with intercooling are used, or the feedstock is highly diluted with hydrogenated product or a diluent that can subsequently be recovered by fractionation. These measures are all expensive and tend to make the cost of highly naphthenic, low aromatic solvents much higher than that of conventional solvents used in the past.